Hi Ken, how are you? Quick answer to your cooling (or lack thereof) woes 1/ Back in The Day, there indeed used to be two water pumps available from Ma Mopar - a non a/c application, and an a/c unit. Today, all of the replacements are heavy-duty a/c units. 2/ if, as you state, your 300 only runs hot while slowed down, in traffic, and is otherwise OK, then the problem is indeed an air circulation problem thru the radiator at low speeds. If the radiator was bad (clogged core, etc. ) then the car would run hot on the highway. Upgrading to a fan shroud / 7 blade fan / thermal fan clutch should indeed solve the problem John Hertog Sag Harbor NY - where overheating is definitely NOT a factor right now! -----Original Message----- From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of baxter Sent: Sunday, December 10, 2006 4:37 PM To: 300 club, listserver Subject: [Chrysler300] improving 65 cooling 65 Service Manual list two different water pumps. one 4.38in dia. 10 blade / another 3.67 in dia. 6 blade. Does anyone know if the distance from back side pump to where fan bolts on, is it the same or different? My water temperature starts rising fast on a hot day in heavy traffic. I'm sure I would have problems on a hot day in a parade. My car is a 65 300 with a 383. with standard cooling package(4 blade fan). I thought I would up grade to AC package by changing to a thermal clutch and 7 blade fan. The local NAPA had a thermal clutch on the shelf. I find it to take up 3 3/8 in. This leaves 1/8 in. between the front of the clutch and the raditor. This is reason for question on water pumps as the 6 blade pump only seems to be used with the thermal clutches. Maybe I should be trying to up grade to trailer package which seems to be only a different fan and box shroud. There were three different fans, std. 4 blade 18 in. / AC 7 blade 18 1/12 in. / Trailer 7 blade 18 in. I have a shroud from a 64 Chrysler New Yorker that I think can be attached. Any suggestion on how I finish the parade on a very hot day with a smile are welcome. Ken Krull Indiana To send a message to this group, send an email to: Chrysler300@xxxxxxxxxxxxxxx For list server instructions, go to http://www.chrysler300club.com/yahoolist/inst.htm For archives go to http://www.forwardlook.net/300-archive/ Yahoo! Groups Links